Large-area organic light-emitting diode (OLED) devices often suffer from the problem of non-uniform light emission. Because of the limited conductivity of the transparent anode layer (e.g., ITO), it is difficult for the injected current to reach the center of the OLED panel from its edge. To overcome this issue, metals have been grid patterned on top of the transparent anode to supply current flows to the center of the panel, resulting in highly uniform light distribution throughout the large-area OLED panel. Park et al., Semicond. Sci. Technol. 26:034002 (2011); Choi et al., Optics Express 19(S4):A793-A803 (2011).
However, the presence of a tall metal grid on top of the transparent anode layer increases the risk of electrical shorts between the metal grid and a cathode. As a results, current industry standard requires a micron-thick insulator (e.g., photoresist) to be coated on the metal grid to prevent electrical shorts. Unfortunately, the requirement of the insulating layer not only complicates the manufacturing processes, but also adversely affects the efficiencies of the OLED device as the insulated metal grid cannot directly deliver the current into the hole injection layer (HIL).
Therefore, a need exists for novel methods of preventing electrical shorts between metal grids and cathodes of large-area OLED devices without using any insulating layer, as well as novel large-area OLED devices with increased efficiencies.